Condensation product of a 2-thiothiazole, formaldehyde, and alkyl phenol to inhibit sulfur corrosive lubricants



Patented Aug. 19, I952 UNITED STATES; rsTENT' OFFICE THIAZULE; F01RMALIDEHYDE", AND ALKYL PHENOLTO INHIBIT SULFURCQBJROSIVE.

LUBRICANTS Richard L. Woodruff; Richmond, and William T.

Stewart andtvarren Lowe, Berkeley, Calif assignors. to. California Research Corporation, SamFrancisco, Calii., a corp oration ofDelaware:

N0. Drawing, Application July 9, 1949, Serial N0. 103,938

Claims;

The present invention relates to lubricatingoils' compounded with active sulfur-containing compounds, such asmetal'isalts of 'thiophosphates; which composite oils are severely corrosive to silver andlike'b'earings; and=to-the prevention of such sulfur: attack" on silverby" incorporating in said severely corrosive compounded oils certain agents; such asa' condensation product of- 2- mercapto benzothiazole, ,formaldehyde and octadecyl phenol Asis- Well known;- the present-day problems involved in the=lubrication-of-internal combustion engines are extremely'complex and difiicult to overcome, due-mainly to" the great loads imposed on:bearings: the'high engine speeds, and the elevated operating;temperatures; To avoid-rapidin a rapid, darkening of'ithe metal surface and formation of sulfides and' the" subsequent sloughing off of the: sulfides duringengine; operation. Thus, thereisa considerable loss ofbearing metal and'a pitting of bearingsurfaces. Thissuliuriattack ,may'be desigrrair'adasi-sulfur-corrosion, as

distinguished from corrosion=caused by action ofacids-and peroxides which are found'as products of oxidation of lubricating oils particularly highly-refined lubricating oils.- This" latter type of corrosion; which may *becalled oxidation corrosion, or acid corrosiong" adversely affects suchhard metal alloys" as cadmium-silver, copper-lead; etc.-, but' does not seriously afiect silver or bronze. Suchoxidation corrosion is usually minimized by-the presence (if-oxidationinhibitors,

which reducethe formation-oi the-corrosive acids and'peroxides.

It is apparent that in spiteof the long desire to lubricate silver bearings \vithlubricants compounded with active sulfur compounds; it has been impractical to-do so in'view' of the aiorementioned-severe corrosivity tosilver.

Therefore; it is anobject of this invention to- 2 provide a non-silver-corrosive -lubricant containing active sulfur compounds;

In the attainment'of thisobject; the present invention concerns a lubricant compounded with active sulfur compounds, which compounded lubricant-is severely corrosiveto silver, and a combination of silver-protective agents which greatly minimi'zeattaclcon silver by sulfur in the compounded lubricant but without adversely-- ai'-- fecting the desired functioning of the sulfurcompounds.

Heretofore, in thel'ubrication of engineshaving' silver metal" wearing surfaces, for example, in certain railroad diesel engines which use silver Wrist pin bushings; it'has beendiifi'cult to prevent sulfur attack of the silver surfaces; Because the silver surfaces (e.- g., the silverwri'st pin bushings) are susceptible toattack by thesulfur' of thesulfur-containing lubricating oil additives, there has been" a tendency to eliminate highly efiective sul fur-containing additives from thediesel lubri catingoils, thereby losing the remarkable-benefits of these additives; As noted hereinabove;

certain highly effective lubricating oil anti oxidants contain sulfur-g which is corrosive-to silver. These effective anti-oxidants have not been used in diesel engines containingsilver wrist pin bushings'with'out sulfur attack-of the silver. Alternative-practices havebeento eliminate the sulfur-containing additivesfrom theoil, allowing the oil to deteriorate more rapidly through oxidation; orthesulfur-containingadditives havebeen included in the-oil formulation, with the resulting sulfur corrosionof the silver-wrist pinbushings. Silver: is also used in wearing surfaces'in aircraft-engines, but-because of the presence of the silver, the highly efiective sulfur-containing aviation oil additivesare not used. Now, however, by using the compounds ofthis invention, lubricating oilscompoundediwith j sulfur-containing additives-can be used in diesel oils, aviation oils, and any other oils where=sul fur corrosionof metals-is' a problem.

It is of extreme advantage t'o use alubricant composition which iseffective not only: ininhibiting oxidation corrosion; but which is. also effective in preventing sulfurattacks onzmeta'ls. In railroad oils, for example, it has been a'ihandi cap to -use1ubricants whichinhibit-corrosion resulting from oxidation products but permit unhampered attack on metals by compoundshaving.

active sulfur present;-

While the outstanding advantages. of the: co-' operative action of thesilver protective agentsdnotherwise severely corrosive-- lubricants containing sulfur compounds is particularly apparent in heavy duty motor oils, the invention combination finds application in turbine oils, gear oils, such as for use in hypoid gears, cutting oils, soluble oils, greases, etc.

The action of the silver protective agents cannot be explained on any simple basis, since their apparent effect appears anomalous: On the one hand, the protective agents prevent destructive attack of the sensitive metal by active sulfur compounds; but, on the other hand, they do not interfere with the functioning of extreme pressure agents which are believed to act by reaction with the metal surface.

The silver protective agents of this invention which reduce the sulfur attack on silver are condensation products obtained by reacting together approximately equimolar amounts of a 2-thiazole compound, formaldehyde and an alkyl phenol. That is, the products obtained by reacting together about equimolar amounts of Z-thiothiazoles, formaldehyde and alkyl phenols are effective in reducing the sulfur attack on silver according to this invention. v

The simplest member of the 2-thio-thiazole group is 2-mercapto-thiazole. Also included are the derivatives of Z-mercapto-thiazole, wherein there may be substituents in the ring carbon atoms.

In 2-thio-thiazole, the hydrogen atoms of the thiazole ring may be substituted by short-chained saturated and unsaturated radicals (e. g., methyl, ethyl, propyl, butyl, ethenyl, propenyl, butenyl, etc.) It is preferred that the substituents contain a total of not more than 20 carbon atoms.

The two adjacent carbon atoms of 2-thiothiazole may form part of a benzene ring, such as in 2-mercapto-benzothiazole. The Z-mercaptobenzothiazole may be substituted on one or more benzene ring carbon atoms by short-chained saturated and unsaturated aliphatic radicals (e. g., methyl, ethyl, propyl, butyl, octyl, ethenyl, propenyl, octenyl, etc.) It is preferred that there be not more than 4 substituent groups on the ring and that these substituents contain a total of not more than 16 carbon atoms.

Examples of 2-thio-thiazoles are: 2-mercaptobenzothiazole; 2--mercapto5-methyl thiazole; Z-mercapto-5-ethyl thiazole; 2-mercapto-4- methyl thiazole; 2-mercapto-4,5-dimethyl thiazole; 2-mercapto-4-ethyl thiazole; 2-mercapto- 4,5-diethyl thiazole; phenyl mercapto-benzothiazole, and methyl mercapto-benzothiazole.

The formaldehyde may be used as such in the reaction, that is, the gaseous formaldehyde, or the aqueous solution of formaldehyde may be used; or compounds which yield formaldehyde, such as paraformaldehyde, may be used in the reaction.

The alkyl groups of the alkyl phenol may be saturated and unsaturated aliphatic groups having from 1 to 24 carbon atoms. The alkyl phenol may have more than 1 alkyl group substituted thereon. It is preferred that the alkyl groups have a total of not more than 32 carbon atoms. Because of the greater effectiveness obtained in the final condensation product as a reactant, it is preferred to use an alkyl phenol containing 1 alkyl group, said alkyl group containing not more than 18 carbon atoms, preferably from 12 to 18 carbon atoms.

Examples of alkyl groups are: methyl, ethyl, propyl, isopropyl, butyl, tertiary-butyl, amyl, tertiary-amyl, octyl, dodecyl, tetradecyl, hexadecyl, octadecyl, butenyl, octenyl, dodecenyl,

'4 tetradecenyl, octadecenyl, butenyl polymers containing from 12 to 16 carbon atoms, etc.

Examples of alkyl phenols are the following: methyl phenol, di-methyl phenol, tri-methyl phenol, iso-propyl phenol, ethyl phenol, di-ethyl phenol, butyl phenol, tertiary-butyl phenol, amyl phenol, di-amyl phenol, tri-amyl phenol, octyl phenol, methyl-octyl phenol, dodecyl phenol, octadecyl phenol, vinyl phenol, butenyl phenol, octadecenyl phenol, polybutylene phenol, wherein the polybutylene group contains from 12 to 16 carbon atoms, condensed ring phenols (such as naphthol and hydroxy anthracene), etc.

The silver protective agents of this invention are effective when they are present in amounts as low as about 0.001% (by weight of total composition). Certain of these compounds have only limited solubility in the lubricating oil and are effective at that solubility. When the protective agents have sufficient solubility, they are effective when each one is used in amounts as great as 5.0%. However, it is preferred that the silver protective agents of this invention be used in amounts sufficient substantially to reduce the corrosion of silver. For example, it is preferred to use these agents in amounts of from about 0.30% to about 1.0%. The major portion of the lubricating composition of this invention is the base oil.

Suitable base oils include a wide variety of lubricating oils such as naphthenic base, paraffin base, and mixed base mineral oils, other hydrocarbon lubricants, e. g., lubricating oil derived from coal products, and synthetic oils, e. g., alkylene polymers (such as polymers of propylene, butylene, etc., and mixtures thereof), alkylene oxide-type polymers, dicarboxylic acid esters and liquid esters of acids of phosphorus. Synthetic oils of the alkylene-oxide type polymer which may be used include those exemplified by the alkylene oxide polymers (e. g., propylene oxide polymers) and derivatives, including alkylene oxide polymers prepared by polymerizing alkylene oxides, e. g., propylene oxide, in the presence of water or alcohols, e. g., ethyl alcohol, and esters of alkylene oxide type polymers, e. g., acetylated propylene oxide polymers prepared by acetylating propylene oxide polymers containing hydroxyl groups.

Synthetic oils of the dicarboxylic acid ester type include those which are prepared by esterifying such dicarboxylic acids as adipic acid, azelaic acid, suberic acid, sebacic acid, alkenyl succinic acid, fumaric acid, maleic acid, etc., with alcohols such as butyl alcohol, hexyl alcohol, Z-ethyl-hexyl alcohol, dodecyl alcohol, etc. Examples of dicarboxylic acid ester synthetic oils include di-butyl adipate, di-hexyl adipate, di-2 ethyl-hexyl sebacate, di-n-hexyl fumarate polymer, etc.

Synthetic oils of the type of liquid esters of the acids of phosphorus include the esters of phosphoric acid, e. g., tricresyl phosphate; the esters of phosphonic acid, e. g., di-ethyl ester of decane phosphonic acid (or other such esters as obtained by reacting alkyl phosphonyl chlorides with hydroxyl-containing compounds such as phenols and aliphatic alcohols, and with olefin oxides such as propylene oxide, as described in Jensen et al. U. S. patent application No. 86,856, now abandoned).

The improved lubricant of the present invention is used wherever elemental sulfur or sulfur compounds containing active sulfur attack metals and are severely corrosive to metals which 5? are being. lubricated: Thus;. as; a result: of f the: present invention, lubricants which normally are severely-corrosive to metal parts .due t'o'attack' by. sulfur or active. sulfur compounds may: now. beused without fear of corrosion byincorporating. therein. a condensation product of a. 2-thio-thiazo1e, formaldehyde and an alkyllphenol. Severely corrosive is defined as thatcore rosion which causes a weight loss greater than. 30;milligrams in the silver' strip test" noted" hereinbelow;

In order to" evaluate the agents of this invention .for. inhibiting. corrosion. due" to: active;v sulfur; a silver stripcorrosion test was made on. numerous agents. of this. invention. This. silver: strip, corrosion.- test was: performed. asfollows:

A silver metalvstrip having" the dimensionsoi- 2 inches by inch by s e inchwas firstcleanedl with aswire' brush untilv the. strip" was highly polished. The strip was Weighed and the weight recorded. This highly polished silver stripwas then placed in a 600 milliliterbeaker' in such a manner that the stri'p was completely immersed when. 300 grams of. the oily being tested was pouredinto the beaker.. The oil was stirred at a temperature of- 300 F. for. 20.hours,- at.which. time. the. silver, strip was removed. andcleaned, first. with chloroform, then. with. petroleum ether. The appearance of the strip was noted. Those strips which had beenv severely attacked were quite black. The testedsi-lver strip was; washed in. 15% aqueous. solution ofpotassium cyanidefor about. 5.minutes..to. remove the-sulfide film adhering. to the strip After. the-striphad-been washed'with potassium. cyanide and dried, it:wasweighed- Thedifierence. in weight of the origi-- nal. strip. and the. strip. after the potassium cyanide-wash was noted; and'recorded asthe; weight lossdue-to corrosion by the sulfur. compound.

Ehe agents, of this. invention are. especially effective as protective agents for silver. However, the protectiveagents' of this invention arealso effective in protecting other sulfur-sensitivemetals from sulfur attack. Such other sulfursensitive metals include-copper, aluminum; and alloys of copper and" aluminum.

As illustrative of various sulfur-containing extreme pressure agents; detergents; oxidation inhibitors; etc.', which cause oils containing them to be severely corrosive to silver, the following. may be mentioned: sulfurized lubricating oils,

Xanthate. esters, chlorinated Xanthate esters,.

diallzyL disulfides. sulfurizedi. fatty oils, metal salts of. reactionproducts of oleiinsandphos phorus pentasulfide, organic trisulfides, tetrae sulfides and pentasulfides (e. g., paraifin wax polysulfide), polyvalent, metal salts: of organesubstitutedacids of phosphorus. (e. g., zinc-hexyle dithiophosphate), sulfurizednlefins (e. g., sulfur? izedv terpene)j, xanthic acid derivatives (e; g., dibutyl .xanthogen disulfide) etc.

Some of theabove-indicated'additives-aremore vigorous in their attack on silver than others, and consequently such attack is more difficult to minimize. However, the silver-protective,agents are advantageously used even with: the. more active sulfur additives.

The silver protective agents of? this-invention.

are also efiective in reducing attack onsilver. by the sulfur in lubricating oils derived from some of the crude oilscharacterizedby their highsulfur content.

Althoughthe silver protective agentsareaespee aeowzsv 6: cially desirable and preferably used in combination with lubricating oils containing the polyvalent metal. salts of organo-substituted thioacids of phosphorus (e. g., zinc cetyl phenyl dithiophosphate), they may be used in lubricatmay be added to-lubricating compositions containing other agents than sulfur-active agents,

that'is, other agents which" are' advantageouslypresentas oiliness agents,- blooming' agents, viscosity index improvers, pour point depressants, peptizing 'agents; etc;

Table I below presents data obtained in' the silver strip test and; shows the remarkable effects which the reaction-product of Example I hereinbelow (the product obtained by reacting together 2-mercapto.-benzothiazole, formaldehyde and an alk-yl phenol) as silver-protective agents: has in reducingthe attack on silver by a California: solvent-refined S. A. E. 30 parafiinic base oil containing sulfurized calcium cetyl -phenate, sulfurized' diparafiin sulfide, calcium' petroleum sulfonateandzinc cetyl phenyl di thiophosphate.

Table I Amount of" Protective SilveeStrip= vAgentused in Test W'eight Lubricating Lossdm- Qil (percentby Milligrams Weight) Table II presents data obtained in the silver strip test of a California solvent-refined S. A. E. BOparafiinic base oil. to which has been added calcium petroleum sulfonate, sulfurized calcium cetyl phenate .and'zinccetyl phenyl di-thiophosphate (using the same: protective agent as in aboveTable I) Table II Amount of Protective Silver Strip; Agent used in. Test Weight Lubricating Loss in O1L(percent by Milligrams;

WVe-ight).

Table'III presents. dataxshowingtheremarkable efiectiveness cf the compounds of thisinvention in.reducing .the severecorrosivcnessof'a solvent.-

refined- S A, E. 30. paraffihbase. oil containing calcium petroleum. sulfonata. sulfurized diparafiin sulfide, a barium dithiophosphate andv tri: octyl. thiophosphate (using, the same. protective agent asin'above Table-1)..

7 Table III Amount of Protective Silver Strip Agent used in Test Weight Lubricating Loss in Oil (percent by Milligrams Weight) Table IV Amount of Protective Silver Strip Agent used in Test Weight Lubricating Loss in Oil (percent by Milligrams Weight) Table V presents data obtained in the silver strip test and shows the effectiveness of the reaction product of Example III herein below (the product obtained by reacting together 2-mer-' capto-benzothiazole, formaldehyde and p-tertiary-butyl phenol) as silver protective agent in reducing the attack of silver by a California solvent-refined S. A. E. 30 parafiinic base oil containing sulfurized calcium cetyl phenate, sulfurized diparaflin sulfide, calcium petroleum sul- The following examples are presented to illustrate the method of preparing the protective agents of this invention. Although the reactants were used in approximately equimolar amounts, it may be desirable in certain instances to use an excess of one of the reactants in order to obtain greater yields of the condensation product.

Example I.--Preparation of the condensation product of 2-meroapto-beneothiazole, formaldehyde and a polybutylene alkylated phenol The "polybutylene alkyl group of the phenol of this example was composed of a mixture of polybutylene groups having from 12 to 16 carbon atoms. The hydroxyl number of the polybutylene alkylated phenol was 151.

A mixture of 20.75 grams of Z-mercapto-benzothiazole, 3.75 grams of para-formaldehye, 46.5

grams of polybutylene alkylated phenol and 2.50 grams of hexamethylene tetramine (used herein as a catalyst) was heated for 40 minutes at a temperature ranging from C. to C. A yellowish-orange colored resinous product was obtained. This product, which has a molecular weight of 560, contained 11.13% sulfur, 2.79% nitrogen, 72.98% carbon and 8.63% hydrogen.

Example II.--Preparation of the condensation product of Z-mercapto-benzothz'azole, formaldehyde and para-tertia'ry-amyl phenol A mixture of 33.4 grams of Z-mercapto-benzothiazole, 33 grams of para-tertiary-amyl phenol, 6 grams of para-formaldehyde and 0.3 gram of hexamethylene tetramine (used herein as a catalyst) was heated for 30 minutes at a temperature ranging from C. to C. A light amber colored resinous product was obtained.

Example III .--Preparati 0n of condensation prodnot of 2-mercapto-benzothiaeole, formaldehyde and para-tertiary-butyl phenol A mixture of 84 grams of Z-mercapto-benzothiazole, 75 grams of para-tertiary-butyl phenol, 15 grams of formaldehyde and 1 gram of hexamethylene tetramine (used herein as catalyst) was heated for 45 minutes at a temperature ranging from 150 C. to 160 C. A light amber colored resinous product was obtained. 7

The data and examples hereinabove show the outstanding effectiveness of the protective agents of this invention in protecting silver from sulfur attack. In addition, the protective agents of this invention also protect silver from selenium attack. That is, lubricants which contain active selenium compounds as additives, for example, dialkyl monoselenides, dialkyl diselenides, dialkyl polyselenides, seleno-mercaptans, metal alkyl selenides, etox, show attack on silver by the selenium. However, the protective agents of this invention inhibit the attack on silver by lubricants containing selenium compounds.

We claim:

1. A lubricant consisting essentially of a major portion of a sulfur-containing lubricating oil composition severely corrosive to silver, and small amounts, sufficient substantially when present in combination to reduce the sulfur attack on silver, of a condensation product obtained by reacting together equal molar proportions of a 2-mercapto-thiazole, formaldehyde and an alkyl phenol wherein the alkyl group is an aliphatic group containing from 12 to 18 carbon atoms at a tempgrature greater than 105 C. for at least 30 minu es.

2. A lubricant consisting essentially of a major portion of a sulfur-containing lubricating oil composition which is severely corrosive to silver, and added to said sulfur-containing lubricating oil composition, a condensation product obtained by reacting together equal molar proportions of a Z-mercapto-thiazole, formaldehyde and an alkyl phenol wherein the alkyl group is an aliphatic group containing from 12 to 18 carbon atoms at a temperature greater than 105 C. for at least 30 minutes.

3. A lubricating oil composition at least 95% of which is composed of an admixture of an oil of lubricating viscosity and lubricating oil additives having present sulfur, which admixture is corrosive to silver, and compounded with this mixture a condensation product obtained by reacting together equal molar proportions of a 2- mercapto-thiazole, formaldehyde and an alkyl '9 phenol wherein the alkyl group is an aliphatic group containing from 12 to 18 carbon atoms at a temperature greater than 105 C. for at least 30 minutes.

4. A lubricant consisting essentially of a major portion of a sulfur-containing lubricating oil composition severely corrosive to silver, and small amounts, suflicient substantially when present in combination to reduce the sulfur attack on silver, of a condensation product obtained by reacting together equal molar proportions of a 2-mercapto-thiazole, wherein the 2 adjacent carbon atoms of the thiazole ring form a part of a benzene ring, formaldehyde and an alkyl phenol, wherein the alkyl group is a polybutylene group of at least 30 minutes.

5. A lubricant consisting essentially of a major portion of a sulfur-containing lubricating oil composition severely corrosive to silver, and small amounts, suflicient substantially when present in combination to reduce the sulfur attack on silver, of a condensation product obtained by reacting together equal molar proportions of 2-mercaptobenzothiazole, formaldehyde and a polybutylene alkylated phenol, wherein the polybutylene group contains from 12 to 16 carbon atoms at a temperature greater than 105 C. for a period of at least 30 minutes.

6. A lubricating oil composition at least 95% of which is composed of an admixture of an oil of lubricating viscosity and lubricating oil additives having present sulfur, which admixture is corrosive to silver, and compounded with this mixture from about 0.4% to about 1% of a condensation product obtained by reacting together equal molar proportions of Z-mercapto-benzothiazole, formaldehyde and a polybutylene alkylated phenol, wherein the polybutylene group contains from 12 to 16 carbon atoms at a temperature 10 greater than 105 C. for a period of at least 30 minutes.

7. A sulfur-containing lubricating oil severely corrosive to silver, and having in said lubricant a condensation product obtained by reacting together equal molar proportions of a Z-mercaptothiazole, wherein the 2 adjacent carbon atoms of the thiazole ring carbons form a part of a henzene ring, formaldehyde and an alkyl phenol wherein the alkyl group is an aliphatic group containing from 12 to 18 carbon atoms at a temperature greater than 105 C. for a period of at least 30 minutes.

8. A sulfur-containing lubricating oil severely corrosive to silver, and small amount, sufficient substantially to reduce the sulfur attack on silver, of a condensation product obtained by reacting together equal molar proportions of 2-mercaptobenzothiazole, formaldehyde and a polybutylene alkylated phenol, wherein the polybutylene group contains from 12 to 16 carbon atoms at a temperature greater than 105 C. for a period of at least 30 minutes.

RICHARD L. WOODRUFF. WILLIAM T. STEWART. WARREN LOWE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,154,096 Loane Apr. 11, 1939 2,201,258 Busse May 21, 1940 2,318,629 Prutton May 11, 1943 2,334,594 Zimmer Nov. 16, 1943 2,384,002 Bayes Sept. 4, 1945 2,414,257 Evans et a1. Jan. 14, 1947 

1. A LUBRICANT CONSISTING ESSENTIALLY OF A MAJOR PORTION OF A SULFUR-CONTAINING LUBRICATING OIL COMPOSITION SEVERLY CORROSIVE TO SILVER, AND SMALL AMOUNTS, SUFFICIENT SUBSTANTIALLY WHEN PRESENT IN COMBINATION TO REDUCE THE SULFUR ATTACK ON SILVER, OF A CONDENSATION PRODUCT OBTAINED BY REACTING TOGETHER EQUAL MOLAR PROPORTIONS OF A 2-MERCAPTO-THIAZOLE, FORMALDEHYDE AND AN ALKYL PHENOL WHEREIN THE ALKYL GROUP IS AN ALIPHATIC GROUP CONTAINING FROM 12 TO 18 CARBON ATOMS AT A TEMPERATURE GREATER THAN 105* C. FOR AT LEAST 30 MINUTES. 